化学修饰对川泽泻凝集素生物学活性和构象的影响

Effects of chemical modification on the biological activity and conformation of the lectin from Alisma plantago-aquatica

用特异性化学修饰和荧光光谱的方法分析川泽泻凝集素(APL)活性位点氨基酸的分布情况.研究结果发现,色氨酸的化学修饰使活性降低80%,统计出每分子APL含有2个色氨酸残基,一个色氨酸位于凝集活性中心,另一个位于分子表面的疏水袋中,与凝集活性无关.精氨酸的化学修饰使活性降低50%,半胱氨酸的化学修饰使活性完全丧失.天冬氨酸、谷氨酸、酪氨酸、丝氨酸/苏氨酸等化学修饰后凝集活性无明显变化.表明色氨酸、精氨酸和半胱氨酸对凝集素的凝集活性中心的构成起重要作用,天冬氨酸、谷氨酸、酪氨酸、丝氨酸/苏氨酸等氨基酸位于凝集素的凝集活性中心附近,只是在维持凝集素分子的构象上具有一定的作用.

This research aimed to study the amino acid distribution of APL in activity site using chemical modification and spectrum analysis. The results showed that Trp-modifiled APL had 80 % of the hemag- glutinating activity lost, and two tryptophan residues in the lectin were calculated. One of the tryptophan residues for bemagglutination activity has a direct role while the other was buried in the hydrophobic shallow groove. The hemagglutinating activity of Arg-modified and Cys-modifiled lectin decreased 50% and 100~, respectively. The modifications of other groups such as Tyr, Glu, Asp and Ser/Thr didn＇t affect the hemagglutinating activity of APL obviously. The results indicated that Trp, Arg and Cys residues were essential to the hemagglutinating activity and were involved in carbohydrate binding site and the Tyr, Glu, Asp and Ser/Thr residues were inessential to the hemagglutinating activity and had the function of maintaining the conformation of APL.